<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    function changeNum(a,b){
      let temp=a
      a=b
      b=temp
      alert(`第一个数是${a}，第二个数是${b}`)
    }
    
    changeNum(1,2)
    changeNum(10,2)
    changeNum(1,29)
    
  </script>
</body>
</html>